/**
 * @program: data_structures_algorithms
 * @description: 合并两有序的单链表
 * @author: lld
 **/
public class SingleLinkedListDemo1 {
    public static void main(String[] args) {
        ListNode l1=new ListNode(1, new ListNode(3, new ListNode(5,null)));
        ListNode l2=new ListNode(1, new ListNode(2, new ListNode(3,null)));
        ListNode listNode = mergeTwoLists(l1, l2);
        System.out.println(listNode);
    }
    public static ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode prehead = new ListNode(-1);

        ListNode prev = prehead;
        while (l1 != null && l2 != null) {
            if (l1.val <= l2.val) {
                prev.next = l1;
                l1 = l1.next;
            } else {
                prev.next = l2;
                l2 = l2.next;
            }
            prev = prev.next;
        }

        // 合并后 l1 和 l2 最多只有一个还未被合并完，我们直接将链表末尾指向未合并完的链表即可
        prev.next = l1 == null ? l2 : l1;

        return prehead.next;
    }
}

class ListNode {
    int val;
    ListNode next;

    ListNode() {
    }

    ListNode(int val) {
        this.val = val;
    }

    ListNode(int val, ListNode next) {
        this.val = val;
        this.next = next;
    }

    @Override
    public String toString() {
        return "ListNode{" +
                "val=" + val +
                ", next=" + next +
                '}';
    }
}



